Prior devices are generally part of the terminal block and are situated at one end or base of the terminal block case. Fixing devices include hooks to enable the apparatus to be installed on or removed from the mounting rail.
French patent 2502449 entitled (in translation) "A fixing device for fixing an apparatus on mounting rails" and filed by the present Applicants, describes a device constituted by a fastening lug which is an integral part of the case of the apparatus and by a fastening piece and a compression spring. The fastening piece comprises a rod and a body which slide along a longitudinal guide in the base of the case. The partially-comressed compression spring is fitted in a housing made in the base and has the rod of the fastening piece passing therethrough, said rod co-operating with the body to form shoulders. The end of the rod is fitted with a pin which compresses the spring when the apparatus is mounted on a rail.
The fastening piece includes two hooks for fixing onto rails, and a guide which cooperates with a groove in the base in order to hold the fastening piece captive. Because it moves in the base of the case, such a fastening piece may not be used as an earthing connection to connect the mounting rail to earth.
An object of the invention is to provide a terminal block fixing device which can also be used as an earthing connection.